Apparatus for the production of lowshrinkage polyethylene terephthalate threads



June 20, 1961 F. KLEEKAMM ET AL 2,988,866

APPARATUS FOR THE PRODUCTION OF LOW-SHRINKAGE POLYETHYLENE TEREPHTHALATE THREADS Original Filed May 5, 1958 FIG.| FIG. 2

INVENTORS:

FRITZ KLEEKAMM ERHARD SIGGEL BY M a ATT'YS United States Patent APPARATUS FOR THE PRODUCTION OF LOW- SHRINKAGE POLYETHYLENE TEREPHTHA- LATE THREADS Fritz Kleekamm, Ohernburg (Main), and Erhard Siggel, Laudenbach (Main), Germany, assignors to- Vereinigte Glanzstoif-Fabrikeu AG., Wuppertal-Elberfeld, Germany Original application May 5, 1958, Ser. No. 733,179. Divided and this application June 10, 1959, Ser. No. 819,428

Claims priority, application Germany May 8, 1957 4 Claims. (CL 57-555) This invention relates to apparatus useful in the production of polyethylene terephthalate threads, which are stretched at predetermined temperatures at different tensions to produce low-shrinkage threads, which threads acquire little or no ring rail period in the spooling thereof on twisting spindles. This is a divisional application of our copending application Serial No. 733,179, filed May 5, 1958.

In the stretching of synthetic threads, a number of processes and devices are known. Some utilize a coldstretching or drawing of the threads, and others use a heat-stretching or drawing. The stretching can be carried out in one, two, or even more steps. A process has been proposed, for example, for the heat-stretching of threads, especially of polyethylene terephthalate, wherein the thread is stretched at a temperature about 30 C. below the melting point, and then is fixed by heat while the thread is maintained under tension at a temperature which is at least as high as the stretching temperature. In this process, the apparatus constitutes a feed roller, a clamping roller loosely mounted on the feed roller, a pair of stretching rollers, of which one roller can be electrically heated, a second pair of stretching rollers, which are used for the heat-fixing of the thread and, finally, take-01f rollers. According to another proposal, the heatstretching of threads of synthetic high-polymers are described, which are to be used as cord. The mechanism necessary for the stretching consists of two rollers of special construction. The rollers have parallel axes, and the first roller can be heated. The rollers have on the surface grooves in the form of circles on the roller, the diameters of which constantly diminish. The yarn on these rollers is first conducted over the grooves of smaller diameter and finally over the grooves of greater diameter, so that, through the differing tension produced, a stretching takes place. Further, it is a known practice to stretch polyester threads in two stages at different temperatures. In the first stage a stretching temperature is maintained, which lies between the so-called seconddegree conversion temperature and the crystallization temperature, with reference in each case to the polyester. In the second stage, the stretching temperature is above the crystallization temperature, at most 50 C. higher. Further, a two-stage stretching of synthetic threads has also been proposed. According to this process the threads are, in principle, stretched by a system of rollers, of which the first roller is heated, while the second roller remains in a cold state. According to another proposal, polyethylene terephthalate threads, in particular, are stretched in two stages. In this process, the thread to be stretched is conducted around a heated, non- Patented June 20, 1961 rotating tension bar, in which process it softens in contact with this bar under the influence of heat, whereupon it is conducted to a fixed heating surface and here it is maintained under a stretching tension to complete the stretch.

The processes and devices that are known, which processes relate to the stretching of threads of synthetic, linear high polymers, illustrate the fact that heretofore an effort was made, in various ways, to arrive at the same goal in the subsequent processing of the threads, namely the improvement of the textile properties of the threads. The various kinds of known processes, however, have limitations with respect to the properties of the finished threads, yarns, etc. For example, these processes are relatively successful in the improvement of strength and elasticity of the threads, but are basically unsuccessful in also providing other desirable textile properties as W6ll,,ViZ., a low-shrinkage of the threads.

In accordance with our invention, it was found that low-shrinkage polyethylene terephthalate threads are obtained, which can be processed at high velocity on a ringtwist machine without significant so -called ring rail period, provided the stretching is carried out in a quite particular manner. In the winding of polyethylene terephthalate threads onto stretch-twist cops by means of a ring rail, periodic stretching and shrinkage variations occur in the thread by reason of the various balloon tensions caused by the winding function. These variations are significant defects and in the dyeing cause a so-called ring rail period to appear. These periodic variations can be recognized easily in the thread by the Frenzelhahndiagram.

For the avoidance of the ring rail period, according to the invention, the thread to be stretched is conducted to a fixed braking bar or rod, heated to to C., on which rod the thread is stretched by drawing it 011 at high velocity. The linear velocity of the thread coming off the braking bar may be varied widely, for example, as low as about 100 meters/min. and may be as high as 400 meters/ min. It is advantageous to operate at as fast a linear speed as possible while maintaining adequate and even heating, stretching, and shrinkage of the threads, and, for this purpose, a linear speed in the range of about 300 meters/min. is to be preferred. The stretch imparted to the threads at or after the braking bar should be in the range of about ZOO-500%, based on the original length of the unstretohed thread.

Then the stretched thread is conducted over a fixing rod heated to to 210 C., and at a linear speed of 5 to 10% less than the said high velocity, linear drawingolf speed, the stretched thread is conducted to a second drawing-01f member to reduce the shrinkage tendency of the thread, whereupon the thread is wound on a cop of a ring-twist device. By the employment of various fixed temperature ranges for the braking rod and the fixing rod, and by the alteration of the drawing-off speeds, the results described above with reference to the textile properties of the threads obtained could be achieved. The apparatus described hereinafter in detail, by its simplicity and accuracy of operation, is eminently suited for the practice of the above-described process.

Referring to the drawing:

FIG. 1 is a semidiagrammatic, front view illustration of a preferred embodiment of the apparatus of our invention; and

FIG. 2 is a semidiagrammatic side view of the apparatus of FIG. 1.

The apparatus illustrated in the drawing is described in conjunction with the use thereof in a specific embodiment of our new process described herein and described and claimed in our aforesaid copending application for better understanding of the invention herein claimed. The utility of our herein described and claimed apparatus, however, is not limited only to said specific embodiment nor to our aforesaid new process.

The unstretched polyethylene terephthalate thread T coming from a supply source such as a bobbin (not shown) is conducted over the heated surface of the braking bar 10, which has a temperature of 125 C. The braking rod is mounted in a metal support 12 and may be heated by any suitable means such as an electrical resistance-heating rod 13 inside the rod 10. After a single looping of the thread around the metal braking rod 10, the thread arrives at the rotatably driven dr-awing-off roller 14, which is composed of a larger cylindrical segment 16 and a smaller cylindrical segment 18. The thread loops several times about the segment 16 in guide grooves 17 and about freely rotatable deflection roller 20, which may be canted slightly with respect to the roller 14 for assisting advancing of the thread loops in a direction from left to right as viewed in FIG. 2. After several loopings over the segment 16, the thread T passes over the fixedly-mounted metal fixing rod or bar 22, similar in construction to bar 10, mounted in support 12 and containing an electrical resistanceheating element 13'. The bar 22 is heated to a temperature of 190 C.

After passing over heated bar 22, the thread T runs to segment 18 of the roller 14. The thread, in grooves 19 of segment 18, loops several times over segment 18 without significant slippage in grooves 19 and roller 20. In this arrangement, the grooves 17 have a greater circumference than grooves 19 and hence have a greater linear speed. The thread coming from the braking bar 10, which first passes several times around segment 16, is drawn off without significant slippage at a rate of 200 m./min., and in the process it is stretched four times its original length (400%). On the other hand, the thread conducted to the segment 18 of the drawing-off roller 14 is reduced in drawing-oif speed by 8% with reference to the linear drawing-off speed of segment 16. This particular reduction in linear speed is achieved by making the circumference of grooves 19 approximately 8% less than the circumference of grooves 17. The reduced linear speed results in a partial relaxation of the thread tension, which reduction of tension in combination with the heat-fixing on bar 22 materially reduces the shrinkage tendencies of the thread over thread spooled directly from the stretch operation on segment 16.-

After leaving segment 18 and roller 20, the thread T passes through guide loop 24 to ring-twist spindle 26 of conventional construction. The basic components of the ring-twist spindle are a cop, illustrated with thread body 28 wound thereon, a vertically reciprocable ring rail 30 with a ring 32 slidably mounted thereon, and a rotatable spindle on which the bobbin is mounted and which is rotatably driven by drive shaft 34. As the spindle and bobbin rotate to wind the thread on the bobbin, the ring 32 travels orbitally about the cop on ring rail 30. This orbital motion imparts a twist to the running thread and causes the running thread to assume a constantly rotating balloon-like curvature B. It is in this balloon-like configuration that the aforesaid ring rail period can occur.

For many purposes, the braking bar 10 provides adequate drag on the running thread to permit a relatively even stretching of the thread. However, if desired, a more delicate, even regulation of the amount of stretch can be provided by the use of a rotatably driven roller 36 about which the thread from the supply source is looped several times so as to be in relatively nonslipping relationship. In this arrangement the initial stretch is determined by the difference in the constant peripheral velocities of the roller 36 and the bases of the grooves 17.

By reason of the high peripheral velocity of the drawing-off roller segment 16, the thread is completely stretched on the braking bar 10. The thread, between stages 14 and 16, can shrink, and it is stabilized by the heat transfer at the fixing bar 22. If the thread were conducted from the drawing-off segment 16 immediately after the complete stretching of about1z4 to the ring-twisting device, then threads would be obtained with a shrinkage upon contact with boiling water of about 10 to 12%. By the fixing of the thread at rod 22, however, together with partial relaxation of the thread due to the difference of peripheral velocities of the segments 16, 18, the thread has a boiling shrinkage of only about 2 to 3%. Through the reduction of the boiling shrinkage to from 2 to 3%, the shrinkage tendency is minimized to such an extent that forces in the thread bringing about the shrinkage no longer manifest themselves when the thread is spooled on the ring-twist cop under the variable ring rail tensions.

The invention is hereby claimed as follows:

1. Apparatus for processing synthetic polymer threads comprising a bar, means for heating said bar to a predetermined temperature, a second bar, means for heating said second bar to a predetermined temperature, a rotatably driven roller having a first group of a plurality of circular grooves, each of equal diameter, and a second group of a plurality of circular grooves, each of equal diameter which is less than the first-mentioned diameter, and a second roller positioned adjacent said rotatably driven roller in substantially parallel relationship, whereby said rotataby driven roller is adapted to draw threads looped in said grooves and over said second roller at different linear velocities from said bars over which the thread passes prior to take-up contact with said roller.

2. An apparatus for processing synthetic polymer threads comprising a fixed bar, means for heating said bar to a surface temperature of about 135 C., a second fixed bar, means for heating said second fixed bar to a surface temperature of about -210 C., a rotatably driven roller with segments each having threadconducting, circular grooves, one segment having circular grooves of a circumference 510% less than the circumference of the circular grooves in the other segment, and a second roller positioned adjacent said first roller with the axes of rotation thereof substantially parallel, whereby said rotatably-driven roller is adapted to draw a continuous thread looped in said grooves and over said second roller at different linear velocities from said bars over which the thread passes prior to take-up contact with the grooves of said rotatably-driven roller.

3. An apparatus for processing synthetic polymer threads comprising a fixed bar, means for heating said bar to a surface temperature of about 80-135 C., a second fixed bar, means for heating said second fixed bar to a surface temperature of about l80-2l0 C., a rotatably driven roller with segments each having threadconducting, circular grooves, one segment having circular grooves of a circumference 5-10% less than the circumference of the circular grooves in the other segment, a second roller positioned adjacent said first roller with the axes of rotation thereof substantially parallel, whereby said rotatably-driven roller is adapted to draw a continuous thread looped in said grooves and over said second roller at different linear velocities from said bars over which the thread passes prior to take-up contact with the grooves of said rotatably-driven roller, and a ringtwist winding device adapted to twist-wind the thread after heat-stretching and heat-fixing thereof.

4. Apparatus for processing synthetic polymer threads comprising a bar, means "for heating said bar to a pre- .5 determined temperature, a second bar, means for heating said second bar to a predetermined temperature, a rotatably driven roller having a first group of a plurality of circular grooves, each of equal diameter, and a second group of a plurality of circular grooves, each of an equal diameter which is less than the first-mentioned diameter, and a second roller positioned adjacent said rotatably driven roller in substantially parallel relationship, whereby said rotatably driven roller is adapted to draw threads looped in said grooves and over said second roller at diflerent linear velocities from said bars over which the thread passes prior to take-up contact with said roller,

and a ring-twist winding device adapted to twist-wind the thread after heat-stretching and heat-fixing thereof.

References Cited in the file of this patent UNITED STATES PATENTS 2,208,497 Coleshill et al. July 16, 1940 2,468,666 Heim Apr. 26, 1949 2,524,439 Green Oct. 3, 1950 FOREIGN PATENTS 628,569 Germany Apr. 7, 1936 

1. APPARATUS FOR PROCESSING SYNTHETIC POLYMER THREADS COMPRISING A BAR, MEANS FOR HEATING SAID BAR TO A PREDETERMINED TEMPERATURE, A SECOND BAR, MEANS FOR HEATING SAID SECOND BAR TO A PREDETERMINED TEMPERATURE, A ROTATABLY DRIVEN ROLLER HAVING A FIRST GROUP OF A PLURALITY OF CIRCULAR GROOVES, EACH OF EQUAL DIAMETER, AND A SECOND GROUP OF A PLURALITY OF CIRCULAR GROOVES, EACH OF EQUAL DIAMETER WHICH IS LESS THAN THE FIRST-MENTIONED DIAMETER, AND A SECOND ROLLER POSITIONED ADJACENT SAID ROTATABLY DRIVEN ROLLER IN SUBSTANTIALLY PARALLEL RELATIONSHIP, WHEREBY SAID ROTATABLY DRIVEN ROLLER IS ADAPTED TO DRAW THREADS 